1. Field of the Invention
The present invention is related to a thin film transistor array, method for manufacturing the thin film transistor array, and an active matrix type display using the thin film transistor array.
2. Description of the Related Art
According to a remarkable development of the information technology, now, information is frequently sent or received using a mobile information terminal, a notebook computer and the like. It is well-known that, in near future, the ubiquitous society will be realized so that information is sent or received at any place. In such a society, an information terminal of thinner and lighter is desired.
Now, main stream of the semiconductor material is silicon type (Si type). However, the research and development of the transistor using an organic semiconductor (the organic transistor) have become active in views of improving the flexibility, reducing the weight and reducing the cost. In the case of the organic semiconductor, process in wet state can be generally adopted. Therefore, there are some advantages of the organic semiconductor. For example, increasing the size is possible, a printing method can be adopted and a plastic substrate can be used. (See non-patent document 1.)
In addition, the application field of the organic semiconductor is wide, and is not limited to the above-mentioned the thin and light flexible display. The application of the organic semiconductor to RFID (radio frequency identification) tag or a sensor is expected. In this way, for the ubiquitous society, the research and development of the organic transistor is necessary.
From these reasons, now, the research and development of the organic semiconductor using a printing method gather attention.
A spin coat method, a dip coat method, an ink jet method and the like are used for forming a semiconductor layer from a solution. In a transistor array having a plurality of arranged transistors which are manufactured by the spin coat method or the dip coat method among the above-mentioned methods, electric current easily flows through a semiconductor layer between transistor devices or between a transistor and a pixel electrode. Therefore, electric current (leak current) value at the off state becomes large, thereby on/off ratio becomes lowered.
Therefore, for example, in patent document 1, transistor devices are separated by forming a semiconductor layer by an ink jet method. In addition, for example, in patent document 2, transistor devices are separated by injecting a semiconductor solution in a channel part between a source electrode and a drain electrode.
In addition, for example, in patent document 3, a pattern is formed using an organic semiconductor solution by flexo printing.
[non-patent document 1] Science Vol. 265, 1684 (1994)
[patent document 1] JP-A-2005-210086
[patent document 2] JP-A-2004-80026
[patent document 3] JP-A-2006-63334